Zapco ASP-Q2 — 7-Band Equalizer and Crossover

Zapco ASP-Q2 — 7-Band Equalizer and Crossover

The ASP-Q2 is a seven-band equalizer with an electronic crossover and a 9.5-volt pre-out. Signal-to-noise is 90dB with THD of 0.03%, and equalization range is ±12dB per band.

It is an analog processor — no DSP, no software, no laptop. Adjustments are made on the unit and take effect immediately.

Seven Bands, Chosen Deliberately

The band frequencies are not evenly spaced octaves. They are placed where car audio problems occur:

• Low: 40Hz – 120Hz
• Bass: 100Hz – 400Hz
• Mid-Bass: 350Hz – 900Hz
• Mid: 650Hz – 1.5kHz
• Mid-High: 1.2kHz – 4.5kHz
• High: 4kHz – 12kHz
• Super-High: 8kHz – 18kHz

Each band's centre frequency is adjustable within its range and overlaps its neighbours, so a problem sitting between two fixed points can still be addressed. That is the practical difference between this and a graphic equalizer with fixed frequencies.

Crossover and Subsonic

A separate subwoofer output has its own crossover adjustable from 30Hz to 300Hz, plus a subsonic filter from 15Hz to 50Hz to protect the woofer from frequencies below what the enclosure can reproduce.

That subsonic range matters for ported enclosures, where the filter should sit just below port tuning — below that point the port stops loading the cone and excursion rises quickly.

9.5-Volt Pre-Out

Maximum output is 7V RMS, with a 9.5-volt pre-out rating. Input impedance is 15 kilohms.

High output voltage improves the signal-to-noise ratio through the run from processor to amplifier. A higher signal level means the amplifier's gain can be set lower, and less gain means less amplification of whatever noise the cable picked up along the way.

System Application

A system that needs equalization and crossover control without adding a digital processor — either because the source is analog, because a laptop-based tune is not wanted, or because the adjustments needed are broad rather than surgical.

Main and Aux inputs allow two sources. The unit runs from 11 to 15 volts DC via a separate power supply module.

Installation Considerations

The unit comes in two pieces: the main chassis at 178 × 33 × 138 mm and a separate power supply at 78 × 24.2 × 57.5 mm. Both need mounting locations, and the main unit needs to be somewhere reachable since all adjustment happens on it.

Set the subsonic filter to the enclosure, not to a default position.

Specifications

• Type: 7-band equalizer with electronic crossover
• Equalization range: ±12dB
• Sub frequency range: 30Hz – 300Hz
• Subsonic frequency range: 15Hz – 50Hz
• S/N ratio: 90dB · THD: 0.03%
• Input impedance: 15 kΩ
• Max output voltage: 7V RMS · 9.5V pre-out
• Power supply: DC 11–15V
• Main unit: 178 × 33 × 138 mm
• Power supply: 78 × 24.2 × 57.5 mm

HF Audio Perspective

An analog equalizer is not a lesser version of a DSP — it is a different tool with different strengths.

Where a system needs broad tonal correction and a subwoofer crossover, and the builder wants adjustments made by hand rather than through software, the ASP-Q2 does that directly. The overlapping band ranges give it more precision than a fixed graphic equalizer, and the 9.5-volt pre-out is a genuine benefit anywhere the signal has a long run to the amplifiers.

What it cannot do is time alignment, and that is the honest limit. A system where driver path lengths need correcting wants a DSP. A system that needs tone shaped and bass crossed over does not necessarily need one.